Steering column and manufacturing method thereof

ABSTRACT

A steering column has an overall hollow and cylindrical shape at least part of which is formed using a column member. The column member includes a main body portion having one-side end section and the other-side end section and a cylindrical member having one-side end section and the other-side section. The cylindrical member is joined in the axial direction with respect to the main body portion by fitting and fastening the other-side end section of the cylindrical member inside the one-side end section of the main body portion. The inner diameter of the end surface of the other-side end section of the cylindrical member is smaller than the inner diameter of a portion of the other-side end section of the cylindrical member. The portion of the other end section of the cylindrical member constitutes a joined section between the main body and the cylindrical member.

TECHNICAL FIELD

The present invention relates to a steering column of an automobilesteering apparatus, and to a manufacturing method thereof.

BACKGROUND ART

As a steering apparatus for applying a steering angle to steered wheels(except in the case of special vehicles such as a forklift, the steeredwheels are normally the front wheels), construction such as illustratedin FIG. 12 is widely known. In this steering apparatus, a steering shaft3 is supported so as to be able to rotate freely on the inner-diameterside of a cylindrical shaped steering column 2 that is supported by thevehicle body 1. A steering wheel 4 is fastened to the rear-end sectionof the steering shaft 3 that protrudes further toward the rear than therear-end opening of the steering column 2. When the steering wheel 4 isrotated, this rotation is transmitted to an input shaft 8 of a steeringgear unit 7 by way of the steering shaft 3, a universal joint 5 a, anintermediate shaft 6 and a universal joint 5 b. As the input shaft 8rotates, a pair of tie rods 9 that are located on both sides of thesteering gear unit 7 are pushed or pulled, which applies a steeringangle to a pair of left and right steered wheels according to the amountthat the steering wheel 4 is operated.

In the construction illustrated in FIG. 12, in order to make it possibleto adjust the forward-backward position of the steering wheel 4, anexpandable and contractible steering column 2 and steering shaft 3 areused. Moreover, during a collision accident, following the primarycollision that occurs when an automobile hits another automobile or thelike, a secondary collision occurs when the body of the driver hits thesteering wheel 4. However, the steering column 2 and steering shaft 3include construction for protecting the driver by absorbing the impactenergy and allowing the steering wheel 4 to displace in the forwarddirection. More specifically, construction is employed in which thesteering shaft 3 that supports the steering wheel 4 is supported by thevehicle body 1 so as to be able to displace in the forward direction dueto an impact load in the forward direction that occurs during asecondary collision. In the construction illustrated in FIG. 12, thesteering shaft 3 includes an outer tube 11 and an inner shaft, andtogether with the outer tube 11 being able to displace in the forwarddirection as the overall length of the steering shaft 3 contracts due toan impact load during a secondary collision, the steering column 2 thatsupports the steering shaft 3 includes an outer column 10 and an innercolumn, and that outer column 10 is supported by the vehicle body 1 sothat the outer column 10 is able to displace in the forward direction asthe overall length of the steering column 2 contracts. It is alsopossible for the front and rear positions of the outer column and innercolumn of the expandable and contractible steering column, and the outertube and inner shaft of the steering shaft to be opposite that of theconstruction illustrated in the figure.

On the other hand, as a countermeasure against theft of an automobile,automobiles are equipped with various kinds of anti-theft apparatuses.As one kind of such an apparatus, a steering lock apparatus, that makesit impossible to operate the steering wheel unless a proper key is used,is widely used. FIG. 13 illustrates construction of an example of asteering lock apparatus as disclosed in JP2008-265646 (A). The steeringlock apparatus 12 is such that a lock unit 13 is provided in part of thesteering column 2 a, and a key lock collar 15, on which an engagementconcave section 14 is formed in at least one location in thecircumferential direction, is fitted onto and fastened to part of thesteering shaft 3 a whose phase in the axial direction coincides withthat of the lock unit 13. When the steering lock apparatus is inoperation (when the key is locked), it is possible to substantiallyunable to rotate the steering shaft 3 a by displacing the tip-endsection of the lock pin 16, that is a component of the lock unit 13,toward the inner diameter side of the steering column 2 a through a lockthrough hole 17 that is formed in the middle section in the axialdirection of the steering column 2 a, and by engaging the tip-endsection of the lock pin 16 with the engagement concave section 14.

When this kind of steering lock apparatus 12 is assembled in a steeringapparatus, the lock unit 13 is provided on the outer-diameter side ofthe steering column 2 a, and the key-lock collar 15 is provided on theinner-diameter side of the steering column 2 a. Therefore, in order toplace the key-lock collar 15 on the inner-diameter side of the steeringcolumn 2 a so as to be able to rotate, and to securely engage ordisengage the lock pin 16 and the key-lock collar 15 without making thestroke of the lock pin 16 too large, it is necessary to make thethickness of the steering column 2 a where the steering lock apparatus12 is assembled thin by making the outer diameter of the steering column2 a small in at least the portion where the steering lock apparatus 12is assembled, and making the inner diameter thereof larger.

FIG. 14 illustrates an outer column 10 a that is a component of asteering column as disclosed in JP2007-223383 (A). In one end section inthe axial direction of the outer column 10 a (the left end section inFIG. 14), the other end section of the cylindrical shaped inner columnis fitted in a state such that relative displacement in the axialdirection is possible. The outer column 10 a is made of a light alloysuch as an aluminum alloy, a magnesium alloy or the like, and is formedinto a single body by casting. A lock through hole 17 a is provided inthe middle section in the axial direction of the outer column 10 a inorder for a steering lock apparatus 12 such as illustrated in FIG. 13 tobe assembled. When the thickness of this kind of outer column 10 a hasbeen made thin, there is a possibility that the strength of the outercolumn, which is essential when the steering lock apparatus 12 isoperated, will not be sufficiently secured. In other words, when tryingto rotate the steering wheel 4 (see FIG. 12) with a large force in astate in which the lock pin 16 that protrudes toward the inner-diameterside of the outer column 10 a through the lock through hole 17 a isengaged with the engagement concave section 14 of the key-lock collar 15(see FIG. 13), an excessively large force is applied to the peripheraledge section of the lock through hole 17 a, and there is a possibilitythat this peripheral edge section will deform. In order to overcome thisproblem, it is feasible to form the outer column 10 a using an ironalloy. However, then another problem occurs such as the weight of theoverall steering column increases.

RELATED LITERATURE Patent Literature

[Patent Literature 1] JP2008-265646 (A)

[Patent Literature 2] JP2007-223383 (A)

SUMMARY OF INVENTION Problem to be Solved by the Invention

In consideration of the situation described above, it is the object ofthe present invention to achieve construction of a steering column inwhich the thickness of part of the steering column can be made thin, andfor which the overall strength can be secured.

Means for Solving the Problems

The steering column of the present invention has an overall hollow andcylindrical shape, and all or part thereof is formed using a columnmember. This column member has:

a main body portion that is made of a light metal alloy such as aluminumalloy, magnesium alloy and the like and that has one-side end sectionand another-side end section; and

a cylindrical member that is made of an iron alloy, that has one-sideend section and another-side end section, and that is joined in theaxial direction with respect to the main body portion by fitting andfastening the other-side end section of the cylindrical member insidethe one-side end section of the main body portion, the inner diameter ofan end surface of the other-side end section of the cylindrical memberbeing smaller than the inner diameter of a portion of the other-side endsection of the cylindrical member that constitutes a joined sectionbetween the main body portion and the cylindrical member. Here, theone-side means one side in the axial direction of the steering column,and the other-side means the opposite side in that axial direction.

Preferably, the inner diameter of the other-side end section of thecylindrical member is equal to or greater than the inner diameter of aportion of the main body portion that is separated in the axialdirection from the joined section.

Moreover, it is preferable to engage a convex section that is providedon the inner circumferential surface of the one-side end section of themain body portion with a concave section that is provided on the outercircumferential surface of the other-side end section of the cylindricalmember.

Alternatively, it is preferable to engage a concave section that isprovided on the inner circumferential surface of the one-side endsection of the main body portion with a convex section that is providedon the outer circumferential surface of the other-side end section ofthe cylindrical member.

The concave section can be at least one concave section that is providedon part in the axial direction of the outer circumferential surface ofthe other-side end section of the cylindrical member, and in part in thecircumferential direction thereof; and is depressed inward in the radialdirection. However, preferably, the concave section is composed of aconcave groove in the axial direction that extends in the axialdirection and is provided in at least one location in thecircumferential direction.

Alternatively or additionally, the concave section can be composed of aconcave groove in the circumferential direction that extends in thecircumferential direction and is provided in at least one location inthe axial direction.

Furthermore, the concave section can be a knurling pattern that isformed by performing a knurling process on the outer circumferentialsurface of the other-side end section of the cylindrical member.

The steering column of the present invention is preferably used in asteering apparatus having a steering lock apparatus, and in that case, alock through hole of the steering apparatus is provided at one locationin the middle section in the axial direction of the cylindrical member.

The manufacturing method for a steering column of the present inventionis characterized in obtaining the column member by the following steps.That is, this method comprises steps of inserting the other-side endsection of the cylindrical member through an insertion hole that is openin one-side end surface of a mold such that the other-side end sectionof cylindrical member protrudes inside the mold; inserting one-side endsection of a core into the other-side end section of the cylindricalmember; obtaining the column member by feeding molten metal into themold and forming the main body portion and joining the one-side endsection of the main body portion to the other-side end section of thecylindrical member by way of the joined section. These steps can beperformed in different orders as long as there is no contradiction.

Preferably, the method for manufacturing a steering column of thepresent invention has a further step of forming the main body portionsuch that the inner diameter of the end surface of the other-side endsection of the cylindrical member is smaller than the inner diameter ofthe portion of the main body portion that is separated in the axialdirection from the joined section, and after forming the main bodyportion, performing a machining process on the inner-diameter sideportion of the tip-end section of the other-side end section of thecylindrical member such that the inner diameter of the other-side endsurface of cylindrical member is equal to or greater than the innerdiameter of the portion of the main body portion that is separated inthe axial direction from the joined section.

In one embodiment of the method for manufacturing a steering column ofthe present invention, a concave section is provided on the outercircumferential surface of the other-side end section of the cylindricalmember, and when forming the main body portion, a convex section isformed on the inner circumferential surface of the one-side end sectionof the main body portion by feeding part of the molten metal into theconcave section. In the case where the concave section is composed ofthe concave groove in the axial direction, it is preferable to form thisconcave groove in the axial direction by a machining process, and in thecase where the concave section is composed of the concave groove in thecircumferential direction, it is preferable to form this concave groovein the circumferential direction by a turning process. On the otherhand, in another embodiment of the method for manufacturing a steeringcolumn of the present invention, a convex section is provided on theouter circumferential surface of the other-side end section of thecylindrical member, and when forming the main body portion, a concavesection is formed on the inner circumferential surface of the one-sideend section of the main body portion by feeding part of the molten metalinto a portion around the convex section.

More preferably, the method for manufacturing a steering column of thepresent invention has a further step of performing a drawing process onthe tip-end section of the other-side end section of the cylindricalmember before inserting the other-side end section of the cylindricalmember through the insertion hole of the mold, and providing the concavegroove in the axial direction on the outer circumferential surface ofthe other-side end section of the cylindrical member at the same time ofmaking the inner diameter of the other-side end surface of thecylindrical member smaller than the inner diameter of the portion of theother-side end section of the cylindrical member that constitutes thejoined section between the main body portion and the cylindrical member.

Particularly, in the case where the concave section is composed of atleast one concave section that is depressed inward in the radialdirection, the concave section can be formed by performing a pressingprocess on the outer circumferential surface of the other-side endsection of the cylindrical member.

In this way, the steering column of the present invention is a steeringcolumn having an overall hollow and cylindrical shape, and the columnmember constituting at least part of this steering column has a mainbody portion that is made of a light metal alloy, and a cylindricalmember that is made of an iron alloy, and is joined in the axialdirection with respect to the main body portion by fitting and fasteningthe other-side end section of the cylindrical member inside the one-sideend section of the main body portion; the inner diameter of theother-side end section of the cylindrical member is equal to or greaterthan the inner diameter of the portion of the main body portion that isseparated in the axial direction from the joined section between themain body portion and the cylindrical member, and the thickness of thecylindrical member is substantially constant except for the innercircumferential edge of the tip-end section of the front-end section ofthe cylindrical member and the rear-end section thereof where a bearingis locked.

The steering apparatus of the present invention has: a steering columnthat is supported by a vehicle body; a steering shaft that is supportedon the inner-diameter side of the steering column so as to be able torotate; and a steering lock apparatus that is provided between thesteering column and the steering shaft, and that substantially preventsthe steering shaft from rotating inside the steering column duringoperation; and particularly, the steering column of the presentinvention is used as this steering column.

Effect of the Invention

With the steering column of the present invention, it is possible tosecure the strength of the steering column while making the thickness ofpart of the steering column thin. In other words, a portion near oneside of the column member constituting this steering column is composedof a cylindrical member that is made of an iron alloy, so it is possibleto secure the strength of the portion near the one side even though thethickness of this portion is made to be thin. On the other hand, theportion near the other side of the column member is composed of a mainbody portion that is made of a light metal alloy such as aluminum alloy,magnesium alloy and the like, so the overall weight of the steeringcolumn does not increase excessively.

Moreover, it is possible to make the inner diameter of at least theother-side end section of the cylindrical member constituting theportion near the one side of the column member of the steering columnlarger than the inner diameter of the portion of the main body portionthat is separated in the axial direction from the joined section betweenthe main body portion and the cylindrical member, except for the tip-endsection of the other-side end section of the cylindrical member.Furthermore, when performing a machining process on the inner diameterof the joined section between the main body portion and the cylindricalmember, except for the tip-end section of the other-side end section ofthe machining is not performed on the cylindrical member having thinthickness, so it is possible to prevent a decrease in strength of thecylindrical member.

In addition, the steering column of the present invention does not havecomplex construction, so can be industrially produced with goodefficiency and at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are partial cross-sectional views illustrating theprocessing order in a method for manufacturing a column member of asteering column of a first example of an embodiment of the presentinvention.

FIG. 2A is an upper half cross-sectional view of a cylindrical memberthat is taken from the first example, and illustrates a state beforeperforming a drawing process on the front-end section; and FIG. 2B is anupper half cross-sectional view of the cylindrical member illustrated inFIG. 2A, and illustrates a state after processing a drawing process onthe front-end section.

FIGS. 3A and 3B are cross-sectional views for explaining problems thatoccur when the manufacturing method of the present invention is notperformed.

FIGS. 4A(a) and 4B(a) illustrate a second example of an embodiment ofthe present invention, and correspond to FIGS. 2A and 2B; FIG. 4A(b) and4B(b) illustrate a third example of an embodiment of the presentinvention, and correspond to FIGS. 2A and 2B; and FIGS. 4A(c) and 4B(c)illustrate a fourth example of an embodiment of the present invention,and correspond to FIGS. 2A and 2B.

FIGS. 5A and 5B illustrate a fifth example of an embodiment of thepresent invention, and correspond to FIGS. 2A and 2B.

FIG. 6A illustrates a sixth example of an embodiment of the presentinvention and corresponds to FIG. 2A; FIG. 6B is of the sixth example,and is a drawing that corresponds to FIG. 2B; FIG. 6C is a side view ofthe cylindrical member that is illustrated in FIG. 6B; and FIG. 6D is across-sectional drawing of section A-A in FIG. 6C.

FIGS. 7A to 7D illustrate a seventh example of an embodiment of thepresent invention, and correspond to FIGS. 6A to 6D.

FIGS. 8A to 8D illustrate an eighth example of an embodiment of thepresent invention, and correspond to FIGS. 6A to 6D.

FIGS. 9A to 9D illustrate a ninth example of an embodiment of thepresent invention, and correspond to FIGS. 6A to 6D.

FIG. 10 is a side view illustrating a steering apparatus of a tenthexample of an embodiment of the present invention.

FIG. 11 is a top view as seen from above in FIG. 10.

FIG. 12 is a perspective view of an example of a conventionally knownsteering apparatus, and illustrates a state in which part is cut away.

FIG. 13 is a simplified cross-sectional view illustrating an example ofconventional construction of a steering lock apparatus.

FIG. 14 is a side view illustrating an example of conventionalconstruction of a steering column in which a lock through hole isprovided.

MODES FOR CARRYING OUT THE INVENTION First Example

FIG. 1A to FIG. 2B illustrate a first example of an embodiment of thepresent invention. A feature of the present invention, including thisexample, is to industrially achieve construction of a steering columnthat is capable of ensuring strength even when the thickness of the rearhalf section (right side in FIGS. 1A to 1C) of an outer column 10 b,which is a column member of the steering column, is thin. Theconstruction and function of the other parts are the same as in aconventional steering column and manufacturing method thereof,therefore, figures and explanations of identical portions will beomitted or simplified such that the following explanation centers on thefeatures of this example.

In this example, the outer column 10 b is formed by joining together inthe axial direction a main body portion 18 that is made of a light alloysuch as an aluminum alloy, magnesium alloy or the like, and acylindrical member 19 that is made of an iron alloy such as carbonsteel. In other words, the front-end section 20, which is the other-sideend section (left side in FIG. 1), of the cylindrical member 19 isfitted inside of and joined to the rear-end section, which is theone-side end section (right side in FIG. 1), of the main body portion18. Therefore, the main body portion 18 forms the front-half section ofthe outer column 10 b, and the cylindrical section 19 forms therear-half section of the outer column 10 b. The main body portion 18corresponds to a portion of the steering column or outer column 10 bthat has construction for being supported by and fastened to the vehiclebody. Moreover, one-side means one side in the axial direction of thesteering column, and the other-side means the opposite side in thataxial direction of the steering column. Where in the example in thefigures, the rear side of the vehicle body corresponds to the one side,and the front side of the vehicle body corresponds to the other side.However, in the present invention, in the case where the cylindricalmember is joined to the front of the main body portion, the front sideof the vehicle body becomes the one side, and the rear side of thevehicle body becomes the other side. Furthermore, construction in whicha cylindrical member is joined to both sides of the main body portion isalso included in the present invention.

In order to manufacture the steering column of this example, byperforming a drawing process on the tip-end section of the front-endsection 20 of the cylindrical member 19, the inner diameter of thefront-end surface 21 of the cylindrical member 19, which is the endsurface of the other-side end section, is made smaller than the portionof the front-end section 20 of the cylindrical member 19 thatconstitutes the joining section between the main body portion 18 and thecylindrical member 19, or in other words, is smaller than the portion ofthe front-end section 20 of the cylindrical member 19 where the drawingprocess was not performed. This portion includes a portion of thefront-end section 20 of the cylindrical member 19 that is located on theinner-diameter side of the portion where the rear-end surface is formed,which is the end surface on the one side of the main body portion 18(portion where the inside end surface of the mold 23 (left side surfaceof the tip-end section of the mold 23 in FIG. 1) is located duringcasting described later), and the portion of the front-end section ofthe cylindrical member 19 where a concave section 22 is formed on theouter circumferential surface. In this example, a concave section 22 isprovided by performing a pressing process at a plurality of locations(four locations in the example in the figure) in the circumferentialdirection of the outer circumferential surface of the front-end section20 of the cylindrical member 19. As illustrated in FIG. 1A, thefront-end section 20 of the cylindrical member 19 is inserted into andfitted inside an insertion hole 25 that is opened in the end surface 24(right-side surface of the tip-end section of the mold 23 in FIG. 1),which is the end surface on the one side of the mold 23, and thefront-end section 20 of the cylindrical member 19 protrudes into themold 23. The shape of the inner circumferential surface, that definesthe insertion hole 25 of the mold 23, matches the outer shape of themain body portion 18 that is obtained by the manufacturing method ofthis example.

Then, a core 26 is inserted inside the insertion hole 25 of the mold 23from the other side (opposite side in the axial direction form the endsurface 24), and the tip-end section 27, which is the one-side endsection of the core 26, is inserted into and fitted inside the front-endsection 20 of the cylindrical member 19. When doing this, a steppedsurface 29 that is provided between the tip-end section 27 and base-endsection 28 of the core 26 comes in contact with the front-end surface 21of the cylindrical member 19. Therefore, the internal space of the mold23 is defined by the inner circumferential surface and inner sidesurface of the mold 23, the front-end surface 21 of the front-endsection 20 and the outer circumferential surface of the cylindricalmember 19, and the outer circumferential surface of the core 26. In thisexample, the front-end surface 21 of the cylindrical member 19 is anopposing surface that comes in contact with the stepped surface 29 ofthe core 26, so as illustrated in FIG. 2A, in the state before thedrawing process is performed on the front-end section of the cylindricalmember 19, a tapered surface section 30 that is inclined in a directionsuch that the outer-diameter dimension becomes smaller going toward thefront end is provided on the outer peripheral edge on the tip end of thefront-end section 20 of the cylindrical member 19. As illustrated inFIG. 2B, by performing a drawing process on the tip-end section of thefront-end section 20 of the cylindrical member 19 that is provided withthis kind of tapered surface 30, the front-end surface 21 of thecylindrical member 19 becomes a surface that is parallel with thestepped surface 29, and the inner peripheral edge around the tip-endsection of the front-end section 20 protrudes inward in the radialdirection (the inner diameter of the front-end surface 21 of thecylindrical member 19 becomes smaller than the inner diameter of aportion of the front-end section 20 of the cylindrical member 19 that islocated on the inner diameter side of a portion where the rear-endsurface of the main body portion 18 is formed, and becomes smaller thanthe inner diameter of the portion where the concave section 22 is formedon the outer circumferential surface thereof).

By feeding molten light alloy such as aluminum alloy, magnesium alloy orthe like into the mold 23 in a state in which the stepped surface 29 ofthe core 26 is in contact with the front-end surface 21 of thecylindrical member 19, the rear-end section of the main body portion 18and the front-end section 20 of the cylindrical member 19 are joined inthe axial direction, and the main body portion 18 is formed. At thistime, by feeding part of the molten metal into the concave section 22 ofthe cylindrical member 19, a convex section 31 is formed on the innercircumferential surface of the rear-end section of the main body portion18. In this example, the joined section between the rear-end section ofthe main body portion 18 and the front-end section of the cylindricalmember 19 are formed by fitting these portions together and by engagingthe concave section 22 and convex section 31. However, construction inwhich the joined section is formed by only one of these is also includedin the present invention. In order to insert the inner shaft into theinner-diameter side of the cylindrical member 19 so as to be able torotate freely, a rolling bearing 33 (see FIG. 13) is provided at therear-end section of the cylindrical member 19. Therefore, in thisexample, a small-diameter section 34 is provided by performing a drawingprocess on the rear-end section of the cylindrical member 19, a steppedsection 38 is provided by performing a machining process on the innercircumferential surface of this small-diameter section 34, and the outerring of the rolling bearing 33 is fitted and fastened inside the steppedsection 38.

After the outer column 10 b that was obtained by forming the main bodyportion 18 is removed from the mold 23, a machining process is performedon the inner peripheral edge of the tip-end section of the front-endsection 20 of the cylindrical member 19 that protrudes further inward inthe radial direction than the inner circumferential surface of the mainbody portion 18, and the inner diameter of the cylindrical member 19 ofat least the portion near the front end (portion except for thesmall-diameter section 34 that was formed for fitting and fastening theouter ring of the rolling-bearing 33 for inserting the inner shaft intothe inner-diameter side of the outer column 10 b so as to be able torotate freely) is made to be equal to or greater than the inner diameterof the portion of the main body portion 18 that is separated in theaxial direction from the joined section between the main body portion 18and the cylindrical member 19 (portion that is fitted around the outsideof the front-end section 20 of the cylindrical section 19). A machiningprocess can be performed on the portion of the main body portion 18 onthe inner-diameter side of the portion that is adjacent in the axialdirection to the joined section until the inner diameter of the mainbody portion 18 of the portion that is separated in the axial directionfrom the joined section is within the range of being equal to or lessthan the inner diameter of the portion near the front end of thecylindrical member 19. By performing this kind of machining process, aforward facing stepped surface between the inner circumferential surfaceof the main body portion 18 through which the inner column 32 is passedthrough and the front-end edge of the cylindrical member 19 iseliminated such that displacement in the forward direction of the outercolumn 10 b during a secondary collision can be performed smoothly, andthus it is possible to more completely protect the driver during acollision accident. Moreover, performing a machining process on theinner-diameter side portion of the rear-end section of the main bodyportion 18 that is adjacent to the joined section is done forconvenience in order to simplify processing, and this kind of machiningprocess can substantially be evaluated as being a machining process thatis performed only on the inner peripheral edge of the front-end sectionof the cylindrical member 19. In this example, the diameter of theinscribed circle of the protrusions in the portion on the innercircumferential surface of the front-end section 20 of the cylindricalmember 19 that corresponds to the concave sections 22 is takenbeforehand to be equal to or greater than the inner diameter of theportion of the main body portion 18 that is separated in the axialdirection from the joined section between the main body portion 18 andthe cylindrical member 19, so regardless of whether or not a machiningprocess is performed on these protrusions, the tip ends of theseprotrusions do not protrude further inward in the radial direction thanthe inner circumferential surface of the main body portion 18.

In the case of the steering column of this example, it is possible tomake the thickness of the rear half section of the outer column 10 b ofthe steering column in which the steering lock apparatus 12 (see FIG.13) is assembled thin, while at the same time ensure the strengththereof. In other words, the rear half section of the outer column 10 bis composed of a cylindrical member 19 that is made of an iron alloy,which is easy to ensure strength. Therefore, even though the thicknessof the cylindrical member 19 that forms the rear half section is madethin, up to 0.4 to 0.75 times, preferably 0.5 to 0.7 times that of thethickness of the main body portion 18 in order to install the lock unit13 or key-lock collar 15, or even though a lock through hole 17 forinserting the lock pin 16 is provided, it is possible to ensure thestrength of the outer column 10 b including the cylindrical member 19.On the other hand, the portion other than the cylindrical member 19 ofthe steering column including the column member (the main body portion18 of the outer column 10 b and the inner column) is made of a lightalloy such as an aluminum alloy, magnesium alloy or the like, and thethickness of the cylindrical member 19 is thin, so there is no excessiveincrease in the weight of the steering column.

Moreover, the concave section 22 that is formed on the outercircumferential surface of the front-end section 20 of the cylindricalmember 19 engages with the convex section 31 that is formed on the innercircumferential surface of the rear-end section of the main body portion18, so it is possible to ensure the joint strength in the axialdirection between the main body portion 18 and the cylindrical member19. Furthermore, in the circumferential direction as well, with the lockpin 16 engaged with the engagement concave section 14 of the key-lockcollar 15, it is possible to improve the torsion rigidity of the joinedsection between the main body portion 18 and cylindrical member 19 dueto the engagement between the concave section 22 and convex section 31even when a large force is applied in an attempt to rotate the steeringwheel 4. Instead of the concave section 22 that is recessed inward inthe radial direction on the outer circumferential surface of thefront-end section 20 of the cylindrical member 19, it is possible toprovide a convex section that protrudes outward in the radial directionto engage with a concave section that is provided on the innercircumferential surface of the rear-end section of the main body portion18.

A drawing process is performed on the tip-end section of the front-endsection 20 of the cylindrical member 19, and with the inner diameter ofthe front-end surface 21 of the cylindrical member 19 less than theinner diameter of the portion of the front-end section 20 of thecylindrical member 19 that is located on the inner-diameter side of theportion where the rear-end surface of the main body portion 18 isformed, the main body portion 18 is formed by casting. Therefore, it ispossible to effectively ensure the strength of the joined sectionbetween the main body portion 18 and the cylindrical member 19. Theadvantage of forming the main body portion 18 in a state in which theinner diameter of the front-end surface 21 of the cylindrical member 19is less than the inner diameter of the portion of the cylindrical member19 that is located on the inner-diameter side of the portion where therear-end surface of the main body portion 18 is formed, will beexplained using FIGS. 3A and 3B in addition to FIGS. 1A to 1C. FIGS. 3Aand 3B illustrate a reference example of manufacturing an outer column10 in which the main body portion 18 a and cylindrical member 19 a arejoined in the axial direction without making the inner diameter of thefront-end surface of the cylindrical member 19 a smaller than the innerdiameter of the portion of the cylindrical member 19 a that is locatedon the inner-diameter side of the portion where the rear-end surface ofthe main body portion 18 a is formed, and in which the inner diameter ofthe cylindrical member 19 a is equal to or greater than the innerdiameter of the main body portion 18 a. As explained in FIGS. 1A to 1C,in order to prevent leakage of molten metal when casting the main bodyportion 18, 18 a, an opposing surface for the stepped surface 29 of thecore 26 to come in contact with is required. In the present invention,the inner diameter of the front-end surface 21 of the cylindrical member19, which is the opposing surface, is made to be smaller than the innerdiameter of the portion of the cylindrical member 19 that is located onthe inner-diameter side of the portion where the rear-end surface of themain body portion 18 is formed, and is made to be smaller than the innerdiameter of the portion where the concave section 22 is formed on theouter circumferential surface thereof.

In this reference example, the inner diameter of the front-end surface21 a of the cylindrical member 19 a is the same as the inner diameter ofthe portion of the cylindrical member 19 a that is located on theinner-diameter side of the portion where the rear-end surface of themain body portion 18 a is formed. Under this kind of condition, asillustrated in FIG. 3A, the inner circumferential surface of the portionnear the rear end of the main body portion 18 a engages with the outercircumferential surface of the portion near the front end of thecylindrical member 19 a, and the main body portion 18 a is formed bycasting. Next, in order for the inner diameter of the cylindrical member19 a to be equal to or greater than the inner diameter of the main bodyportion 18 a, as illustrated in FIG. 3B, a machining process isperformed on the inner-diameter side portion of the front-end section 20a of the cylindrical member 19 a in the joined section between the mainbody portion 18 a and the cylindrical member 19 a. When performing thismachining process, the inner diameter of the front-end surface 21 a ofthe cylindrical member 19 a is not smaller than the inner diameter ofthe portion of the cylindrical member 19 a that is located on theinner-diameter side of the portion where the rear-end surface of themain body portion 18 a is formed, so not only the portion on theinner-diameter side of the joined section between the main body portion18 a and the cylindrical member 19 a (portion where the rear-end surfaceof the main body portion is formed) of the cylindrical member 19 a, butalso the portion on the inner-diameter side of the portion that islocated further on the rear-end side than this joined section is cutaway. The thickness of the cylindrical member 19 a is thin, so when theportion on the inner-diameter side of the portion near the front endthereof is cut away, the thickness of the cylindrical member 19 abecomes too thin in the portion that is located in the joined sectionand further on the rear-end side than the joined section, and thus it isnot possible to ensure joint strength of the joined section or to ensurethe torsion strength and bending strength of the portion that is locatedfurther on the rear-end side than the joined section.

On the other hand, in the construction of the first example, whenperforming a machining process on the portion on the inner-diameter sideof the joined section between the main body portion 18 and thecylindrical member 19, the portions where this machining process isperformed are only the peripheral edge of the tip-end section of thefront-end section 20 of the cylindrical member 19, and the portion ofthe inner-diameter side portion of the main body portion 18 that isadjacent to the joined section between the main body portion 18 and thecylindrical member 19. Except for the tip-end section of the front-endsection 20, it is not necessary to machine away the joined section,including the portion of the cylindrical member 19 that is locatedfurther on the rear-end side than the joined section. Therefore, asillustrated in FIG. 1C, it is possible to sufficiently ensure thestrength of the joined section between the main body portion 18 and thecylindrical member 19, and the torsion strength and bending strength ofthe cylindrical member 19 even in a state in which the inner peripheraledge of the tip-end section of the front-end section 20 of thecylindrical member 19 has been machined away.

Moreover, a machining process is performed on the inner peripheral edgeof the tip-end section of the front-end section 20 of the cylindricalmember 19, and the inner diameter of the portion near the front end ofthe cylindrical member 19 is equal to or greater than the inner diameterof the portion of the main body portion 18 that is separated in theaxial direction from the joined section. The cylindrical inner column 32is fitted inside the front-end section (left-end section in FIGS. 1A to1C) of this kind of outer column 10 b in a state such that displacementin the axial direction is possible, to construct an expandable andcontractible steering column. The inner diameter of the outer column 10b becomes larger from the front side (left side in FIGS. 1A to 1C) inthe order of the main body portion 18 and cylindrical member 19, so whenthe outer column 10 b displaces forward in the axial direction relativeto the inner column 32 due to forward-backward position adjustment ofthe steering wheel, or due to a secondary collision, it is possible tosuppress the possibility that the rear-end edge of the inner column 32interferes with the portion that protrudes from the innercircumferential surface of the outer column 10 b, and thus displacementin the forward direction of the steering wheel will be obstructed. Theposition in the axial direction of the small-diameter section 34 is suchthat the rear-end edge of the inner column 32 does not interfere withthe inner circumferential surface of the small-diameter section 34 evenwhen a secondary collision advances.

Moreover, during manufacturing, the inner diameter of the front-endsurface 21 of the cylindrical member 19 is made to be less than theportion of the cylindrical member 19 that is located on theinner-diameter side of the portion where the rear-end surface of themain body portion 18 is formed, so when forming the main body portion 18by feeding molten light alloy into the mold 23, the molten metal is notfed into the inner circumferential side of the cylindrical member 19,and the inner circumferential surface of the cylindrical member 19 isprevented from becoming a rough surface due to light alloy adhering tothe surface.

Second Example to Fourth Example

FIGS. 4A(a to c) and 4B(a to c) illustrate second to fourth examples ofan embodiment of the present invention. In the figures from FIG. 4A(a)to FIG. 4B(c), the states before processing the tip-end section of thefront-end section 20 are illustrated in FIGS. 4A(a to c), and the statesafter the processing are illustrated in FIG. 4B(a to c). In theseexamples, the shape of the cylindrical member 19 b to 19 d differs fromthat in the first example. First, in the case of the second exampleillustrated in FIGS. 4A(a) and 4B(a), in the state before a drawingprocess is performed on the tip-end section of the front-end section 20of the cylindrical member 19 b, there is no tapered surface section 30(see FIGS. 2A and 2B) such as provided in the first example. Therefore,when the drawing process is performed on the tip-end section of thefront-end section 20 of the cylindrical member 19 b, the front-end edgeof the cylindrical member 19 b becomes a shape in which the middlesection in the radial direction is pointed toward the front. There is noparticular problem in this case as long as the dimension in the radialdirection of the stepped surface 29 of the core 26 (see FIGS. 1A to 1C)is sufficiently large. It is also possible to make the front-end surfaceof the cylindrical member 19 b into a surface that is parallel with thestepped surface 29 by performing a machining process on the front-endedge after performing the drawing process on the tip-end section of thefront-end section 20 of the cylindrical member 19 b.

In the case of the third example illustrated in FIG. 4A(b) and FIG.4B(b), by performing a drawing process on the tip-end section of thefront-end section 20 of the cylindrical member 19 c, a small-diametersection 35, having an inner diameter that is smaller than the portion ofthe cylindrical member 19 c that is located on the inner-diameter sideof the portion where the rear-end surface of the main body portion 18 isformed, is provided on the tip-end section of the front-end section 20.Moreover, in the fourth example illustrated in FIG. 4A(c) and FIG.4B(c), by performing a bending process on the tip-end section of thefront-end section 20 of the cylindrical member 19 d, an inward facingflange-shaped circular-ring section 36 is provided on the front-end edgeof the cylindrical member 19 d. Except for the differences in the shapesof the tip-end sections of the front-end section 20 of the cylindricalmembers 19 b to 19 d, the other construction and functions are the sameas in the first example.

Fifth Example

FIGS. 5A and 5B illustrate a fifth example of an embodiment of thepresent invention. In this example, by bending the entire front-end edgeof the cylindrical member 19 e into a shape having a circular arc shapedcross section, a protruding piece section 37, whose inner diameterthereof is less and the outer diameter thereof is larger than theinner-diameter side portion where the rear-end surface of the main bodyportion 18 is formed (see FIGS. 1A to 1C). Moreover, a cut-out section40 is provided in at least one location in the circumferential directionof the portion near the outer diameter of the protruding piece section37. When casting the main body portion 18, the stepped surface 29 of thecore 26 (see FIGS. 1A and 1B) comes in contact with the protruding piecesection 37. The half section on inner-diameter side of the protrudingpiece section 37 is cut and removed after casting of the main bodyportion 18. In the sate after casting of the main body portion 18, thejoint strength in the axial direction is ensured by the engagementbetween the half section on the outer-diameter side of the protrudingpiece section 37 and the main body portion 18. Furthermore, the jointstrength in the circumferential direction is ensured by the engagementbetween the cut-out section 40 of the half section on the outer-diameterside of the protruding piece section 37 and the main body portion 18that enters inside of the cut-away section 40.

In this example, in order to provide the outer ring of the rollingbearing 33 (see FIG. 13) on the inner-diameter side of the cylindricalmember 19 e, a fastening section 39 that protrudes toward the innercircumferential surface of the cylindrical member 19 e is provided byperforming a pressing process at plural locations in the circumferentialdirection on the rear-end section of the cylindrical member 19 e, andthe outer ring of the rolling bearing 33 is fastened to the fasteningsection 39. The construction and function of the other parts are thesame as in the first example.

Sixth Example

FIGS. 6A to 6D illustrate a sixth example of an embodiment of thepresent invention. In this example, concave grooves 41 that are formedin the circumferential direction around the entire circumference areprovided at a plurality of locations (three locations in the figures) inthe axial direction of the outer circumferential surface of thefront-end section 20 of the cylindrical member 19 f. Moreover, concavegrooves 42 that extend in the axial direction are provided at aplurality of locations in the circumferential direction of the outercircumferential of the front-end section 20 of the cylindrical member 19f. A drawing process is performed on the tip-end section of thefront-end section 20 of the cylindrical member 19 f to increase therigidity, so large elastic deformation of the outer circumferentialsurface of the front-end section 20 of the cylindrical member 19 f,which is a processed part, is suppressed. Therefore, for example, whenforming the concave grooves 41 in the circumferential direction on theouter circumferential surface of the front-end section 20 of thecylindrical member 19 f by a turning process, and forming the concavegrooves 42 in the axial direction by a machining process, it is possibleto form the concave grooves 41 in the circumferential direction and theconcave grooves 42 in the axial direction easily and highly precisely.Moreover, when forming the cylindrical member 19 f by cutting a longpipe material into a specified length by a turning process, it is alsopossible to form the concave grooves 41 in the circumferential directionin the same process without removing a chuck by performing a so-calledone-chuck turning process. In this case, it is possible to reduce themanufacturing cost by reducing the manufacturing processes.

When placing the cylindrical member 19 f into the mold 23 and formingthe main body portion 18 (see FIGS. 1A to 1C) by feeding molten lightalloy, part of the molten metal is fed into the concave grooves 41 inthe circumferential direction and concave grooves 42 in the axialdirection, thus forms protrusions in the circumferential direction onthe inner circumferential surface and protrusions in the axial directionon the outer circumferential surface of the rear-end section of the mainbody portion 18. In this example, the joint strength in the axialdirection between the main body portion 18 and the cylindrical member 19f is ensured by the engagement between the concave grooves 41 in thecircumferential direction and the protrusions in the circumferentialdirection, and the torsion rigidity of the main body portion 18 and thecylindrical member 19 f is ensured (relative rotation of these membersis prevented) by the engagement between the concave grooves 42 in theaxial direction and the protrusions in the axial direction. This examplecan be implemented in combination with the construction of one of thesecond example to fourth example. The construction and functions of theother parts are the same as in the first example.

Seventh Example

FIGS. 7A to 7D illustrate a seventh example of an embodiment of thepresent invention. In this example, of the outer circumferential surfaceof the front-end section of the cylindrical member 19 g, a concavegroove 41 a in the circumferential direction is provided around theentire circumference at one location in the middle section in the axialdirection of concave grooves 42 a that are provided at a plurality oflocations in the circumferential direction. This kind of concave groove41 a in the circumferential direction is formed by performing a rollingprocess or pressing process that presses and plastically deforms theouter circumferential surface of the front-end section 20 of thecylindrical member 19 g inward in the radial direction. Moreover, theconcave grooves 42 a in the axial direction are formed by performing arolling process or drawing process on the front-end section 20 of thecylindrical member 19 g. By forming the concave groove 41 a in thecircumferential direction and concave grooves 42 a in the axialdirection by plastic deformation, it is possible to keep the reductionin the plate thickness of the processed portion small, and thus cuttingof the fiber flow (fiber-shaped metal structure) is prevented.Therefore, the rigidity of the cylindrical member 19 g at the joinedsection between the main body portion 18 (see FIGS. 1A to 1C) and thecylindrical member 19 g is ensured even when the plate thickness of thecylindrical member 19 g is thin.

Moreover, when performing the drawing process on the tip-end section ofthe front-end section 20 of the cylindrical member 19 g, it is possibleto form the concave grooves 42 a in the axial direction at the same timeby a drawing process. In this case, it is possible to reduce themanufacturing cost by reducing the manufacturing processes. When formingthe concave groove 41 a in the circumferential direction by a pressingprocess and forming the concave grooves 42 a in the axial direction by adrawing process, the diameter of the inscribed circle of protrusionsthat are located in portions on the inner circumferential surface of thefront-end section 20 of the cylindrical member 19 f that correspond tothe concave groove 41 a in the circumferential direction and concavegrooves 42 a in the axial direction is equal to or greater than theinner diameter of the portion of the main body portion 18 that isseparated from the joined section between the main body portion 18 andthe cylindrical member 19, and the tip-end sections of these protrusionsdo not protrude further inward in the radial direction than the innercircumferential surface of the main body portion 18. The constructionand function of the other parts are the same as in the sixth example.

Eighth Example

FIGS. 8A to 8D illustrate an eighth example of an embodiment of thepresent invention. In this example, of the outer circumferential surfaceof the front-end section 20 of the cylindrical member 19 h, concavegrooves 42 b are provided at a plurality of locations in thecircumferential direction, and a concave groove 41 b in thecircumferential direction is provided around the entire circumference atone location in the portion that is adjacent to the rear side in theaxial direction of the portion where the concave grooves 42 b in theaxial direction are formed. The construction and function of the otherparts are the same as in the seventh example.

Ninth Example

FIGS. 9A to 9D illustrate a ninth example of an embodiment of thepresent invention. In this example, a rough surface section 43 isprovided on the outer circumferential surface of the front-end section20 of the cylindrical member 19 i by performing a knurling process onthe outer circumferential surface of the front-end section 20 of thecylindrical member 19 i. The knurling pattern that is formed by thisknurling process can be a flat pattern (straight pattern), or aninclined pattern (spiral pattern), however, as illustrated in FIG. 9C,preferably a twill pattern is formed in which small concave grooves thatare inclined in both the circumferential direction and axial direction(the inclination angle with respect to the axial direction is 10° to80°, preferably 30° to 60°, and most preferably 45°) cross in a net-likepattern. In other words, by forming a twill shaped knurling pattern, inaddition to increasing the torsion rigidity of the cylindrical member 19i and the main body portion 18 (see FIGS. 1A to 1C) and being able toprevent relative rotation between the cylindrical member 19 i and themain body portion 18, the joint strength in the axial direction betweenthe cylindrical member 19 i and the main body portion 18 is increased,and it is possible to prevent the cylindrical member 19 i from fallingout from the main body portion 18.

The knurling pattern can be formed by a rolling process, however,preferably is formed by a machining process. In other words, whenforming a knurling pattern on the outer circumferential surface of thefront-end section of the cylindrical member 19 i, which is a pipematerial having a thin thickness, using a rolling process, there is apossibility that the outer circumferential surface of the front-endsection of the cylindrical member 19 i, where the rolling process isperformed, will deform (warp). On the other hand, by forming a knurlingpattern by a machining process, deformation of the portion wheremachining process is performed is prevented, and the rough surfacesection 43 can be formed easily and highly precisely. As a method forforming the knurling pattern with this kind of machining process, forexample, Quick Knurling by Yamada Engineering Co., Ltd. can be employed.

In the ninth example, a rough surface section 43 for preventing relativerotation between the cylindrical member 19 i and the main body portion18 and for preventing the cylindrical member 19 i from falling out ofthe main body portion 18 is formed by a knurling process, so it ispossible to ensure the plate thickness of the cylindrical member 19 i atthe joined section between the main body portion 18 and the cylindricalmember 19 i, and ensure the rigidity of the joined section. In otherwords, when a concave groove 41 in the circumferential direction isformed by a turning process, and concave grooves 42 in the axialdirection are formed by a machining process as in the case of the sixthexample, if the plate thickness of the cylindrical member 19 is notsufficiently thick, the plate thickness of the cylindrical member 19 atthe joined section between the main body portion 18 and the cylindricalmember 19 will become thin, and there is a possibility that the rigidityof the joined section will not be sufficiently ensured. However, in thisexample, by forming a knurling pattern that is composed of numerousshallow infinitesimal concave grooves on the outer circumferentialsurface of the front-end section 20 of the cylindrical member 19 i,relative rotation and falling out is prevented. The construction andfunction of the other parts is the same as in the first example.

Tenth Example

FIG. 10 and FIG. 11 illustrate a tenth example of an embodiment of thepresent invention. This example is an example of the steering apparatusof the present invention. This steering apparatus is an impact absorbingsteering apparatus that comprises a telescopic mechanism. In thissteering apparatus, the rear-end section of an inner column 32 a isfitted inside the front-end section of an outer column 10 d in a statein which both of the outer column 10 d and inner column 32 a are able todisplace in the axial direction. A housing 44 for housing a reductiongear that comprises an electric power-steering apparatus is connectedand fastened to the front-end section of the inner column 32 a. Thiskind of steering column 2 b is supported by the vehicle body connectingand fastening a rear-side bracket 45, which supports the outer column 10d, and a front-side bracket 46, which is provided on both the left andright side of the front-end section of the housing 44, to the vehiclebody. In this example, a steering column that includes a column memberof one of the first to ninth examples is used as the outer column 10 bthat comprises the steering column 2 b.

Furthermore, a steering lock apparatus such as illustrated in FIG. 13 isassembled in the steering apparatus of this example. When the steeringlock apparatus is operated, the steering shaft 3 is substantiallyprevented from rotating inside the steering column 2 b. Beingsubstantially prevented means that when the steering wheel 4 (see FIG.12) is rotated with a specified force or greater, or specifically, witha force that is greater than a value specified by the key-lockregulation, in a state where the engagement concave section 14 isengaged with the tip-end section of the lock pin 16 (see FIG. 13) whenthe key is locked, the steering shaft 3 is allowed to rotate withrespect to the key-lock collar 15 and the steering column 2 b. However,the steering shaft 3 will not rotate by applying a force to the steeringwheel 4 to the same degree as of the force applied in a normal drivingposition in order to apply a desired angle to the steered wheels. Thecolumn member of the present invention is not limited to the outercolumn of a steering column comprising a telescopic mechanism asdescribed above, and can also be applied to a steering column that doesnot comprise a telescopic mechanism.

EXPLANATION OF THE REFERENCE NUMBERS

-   1 Vehicle body-   2, 2 a to 2 b Steering column-   3, 3 a Steering shaft-   4 Steering wheel-   5 a, 5 b Universal joint-   6 Intermediate shaft-   7 Steering gear unit-   8 Input shaft-   9 Tie rod-   10, 10 a to 10 d Outer column-   11 Outer tube-   12 Steering lock apparatus-   13 Lock unit-   14 Engagement concave section-   15 Key-lock collar-   16 Lock pin-   17, 17 a Lock through hole-   18, 18 a Main body portion-   19, 19 a to 19 i Cylindrical member-   20 Front-end section-   21 Front-end surface-   22 Concave section-   23 Mold-   24 End surface-   25 Insertion hole-   26 Core-   27 Tip-end section-   28 Base-end section-   29 Stepped surface-   30 Tapered surface section-   31 Convex section-   32, 32 a Inner column-   33 Rolling bearing-   34 Small-diameter section-   35 Small-diameter section-   36 Circular-ring section-   37 Protruding piece section-   38 Stepped section-   39 Fastening section-   40 Cut-out section-   41, 41 a, 41 b Concave groove in the circumferential direction-   42, 42 a, 42 b Concave groove in the axial direction-   43 Rough surface section-   44 Housing-   45 Rear-side bracket-   46 Front-side bracket

1. A steering column having an overall hollow and cylindrical shape atleast part of which is formed using a column member, the column membercomprising: a main body portion made of a light metal alloy, the mainbody having one-side end section and another-side end section; and acylindrical member made of an iron alloy, the cylindrical member havingone-side end section and another-side end section, the cylindricalmember being joined in an axial direction with respect to the main bodyportion by fitting and fastening the other-side end section of thecylindrical member inside the one-side end section of the main bodyportion, an inner diameter of an end surface of the other-side endsection of the cylindrical member being smaller than an inner diameterof a portion of the other-side end section of the cylindrical member,the portion of the other-side end section of the cylindrical memberconstituting a joined section between the main body portion and thecylindrical member; wherein the main body portion has a convex sectionor concave section on an inner circumferential surface of the one-sideend section of the main body portion, and the cylindrical member has aconcave section or convex section that engages with the convex sectionor concave section of the main body portion on an outer circumferentialsurface of the other-side end section of the cylindrical member; and thecolumn member is obtained by: forming the concave section or convexsection on the outer circumferential surface of the other-side endsection of the cylindrical member; inserting the other-side end sectionof the cylindrical member through an insertion hole opened in one-sideend surface of a mold, such that the other-side end section of thecylindrical member protrudes inside the mold; inserting one-side endsection of a core into the other-side end section of the cylindricalmember; and feeding molten metal into the mold and forming the main bodyportion, forming the convex section or concave section on the innercircumferential surface of the one-side end section of the main bodyportion to join the one-side end section of the main body portion andthe other-side end section of the cylindrical member in the axialdirection via the joined section.
 2. The steering column according toclaim 1, wherein the concave section is composed of a concave groove inthe axial direction, the concave groove in the axial direction extendingin the axial direction and provided in at least one location in thecircumferential direction.
 3. The steering column according to claim 1,wherein the concave section is composed of a concave groove in thecircumferential direction, the concave groove in the circumferentialdirection extending in the circumferential direction and provided in atleast one location in the axial direction.
 4. The steering columnaccording to claim 1, wherein the concave section is provided on theouter circumferential surface of the other-side end section of thecylindrical member.
 5. The steering column according to claim 1, whereinan inner diameter of the other-side end section of the cylindricalmember is equal to or greater than an inner diameter of the portion ofthe main body portion, the portion of the main body portion beingseparated in the axial direction from the joined section.
 6. Thesteering column according to claim 1, wherein a drawing process orbending formation is performed on the tip-end section of the other-sideend section of the cylindrical member to form an arc shape in the crosssection, and a machining process is performed on the portion on theinner-diameter side of the tip-end section of the other-side end sectionof the cylindrical member.
 7. The steering column according to claim 1,wherein a machining process is not performed on a portion of theother-side end section of the cylindrical member except for the tip-endsection.
 8. The steering column according to claim 1, wherein thecylindrical member has a lock through hole that is a component member ofa steering lock apparatus at one location in a middle section in theaxial direction of the cylindrical member.
 9. A method for manufacturingthe steering column of claim 1, comprising steps of: forming the concavesection or convex section on the outer circumferential surface of theother-side end section of the cylindrical member; inserting theother-side end section of the cylindrical member through the insertionhole opened on the one-side end surface of the mold such that theother-side end of cylindrical member protrudes inside the mold;inserting the one-side end section of the core into the other-side endsection of the cylindrical member; feeding molten metal into the moldand forming the main body portion, forming the convex section or concavesection on the inner circumferential surface of the one-side end sectionof the main body portion to join the one-side end section of the mainbody portion and the other-side end section of the cylindrical member inthe axial direction via the joined section so as to obtain the columnmember.
 10. The method for manufacturing a steering column according toclaim 9, further comprising steps of: forming the main body portion suchthat the inner diameter of the end surface of the other-side end sectionof the cylindrical member is smaller than the inner diameter of theportion of the main body portion separated in the axial direction fromthe joined section, and after forming the main body portion, performinga machining process on the portion on the inner-diameter side of thetip-end section of the other-side end section of the cylindrical membersuch that the inner diameter of the other-side end surface ofcylindrical member is equal to or greater than the inner diameter of theportion of the main body portion separated in the axial direction fromthe joined section.
 11. The method for manufacturing a steering columnaccording to claim 9, further comprising steps of: providing the concavesection on the outer circumferential surface of the other-side endsection of the cylindrical member, and forming the convex section on theinner circumferential surface of the one-side end section of the mainbody portion by feeding part of the molten metal into the concavesection when forming the main body portion.
 12. The method formanufacturing a steering column according to claim 11, wherein theconcave section is composed of a concave groove in the axial direction,the concave groove in the axial direction extending in the axialdirection and provided in at least one location in the circumferentialdirection, and the method further comprises a step of forming theconcave groove in the axial direction by a machining process.
 13. Themethod for manufacturing a steering column according to claim 12 furthercomprising a step of performing a drawing process on the tip-end sectionof the other-side end section of the cylindrical member before insertingthe other-side end section of the cylindrical member through theinsertion hole of the mold, and providing the concave groove in theaxial direction on the outer circumferential surface of the other-sideend section of the cylindrical member at the same time of making theinner diameter of the other-side end surface of the cylindrical membersmaller than the inner diameter of the portion of the other-side endsection of the cylindrical member, the portion of the other-side endsection of the cylindrical member forming the joined section between themain body portion and the cylindrical member.
 14. The method formanufacturing a steering column according to claim 11, wherein theconcave section is composed of a concave groove in the circumferentialdirection, the concave groove in the circumferential direction extendingin the circumferential direction and provided in at least one locationin the axial direction, and the method further comprises a step offorming the concave groove in the circumferential direction by a turningprocess.
 15. The method for manufacturing a steering column according toclaim 11, wherein the concave section is composed of a knurling patternformed on the outer circumferential surface of the other-side endsection of the cylindrical member, and the method further comprises astep of forming the knurling pattern by performing a knurling process onthe outer circumferential surface of the other-side end section of thecylindrical member.
 16. The method for manufacturing a steering columnaccording to claim 11, further comprising a step of forming the concavesection by performing a pressing process on the outer circumferentialsurface of the other-side end section of the cylindrical member.
 17. Themethod for manufacturing a steering column according to claim 9, whereinthe convex section is provided on the outer circumferential surface ofthe other-side end section of the cylindrical member, and the methodfurther comprises a step of forming the concave section on the innercircumferential surface of the one-side end section of the main bodyportion by feeding part of the molten metal into a portion around theconvex section when forming the main body portion by feeding moltenmetal into the mold.
 18. A steering apparatus comprising: a steeringcolumn supported by a vehicle body; a steering shaft supported on theinner-diameter side of the steering column so as to be able to rotate;and a steering lock apparatus provided between the steering column andthe steering shaft, the steering lock apparatus substantially preventingthe steering shaft from rotating inside the steering column duringoperation, wherein the steering column is the steering column accordingto claim 8.